{"453401":{"#nid":"453401","#data":{"type":"news","title":"Disappearing Carbon Circuits on Graphene Could Have Security, Biomedical Uses","body":[{"value":"\u003Cp\u003EIn the television drama \u201cMission Impossible,\u201d instructions for the mission were delivered on an audio tape that destroyed itself immediately after being played. Should that series ever be revived, its producers might want to talk with Georgia Institute of Technology professor Andrei Fedorov about using his \u201cdisappearing circuits\u201d to deliver the instructions.\u003C\/p\u003E\u003Cp\u003EUsing carbon atoms deposited on graphene with a focused electron beam process, Fedorov and collaborators have demonstrated a technique for creating dynamic patterns on graphene surfaces. The patterns could be used to make reconfigurable electronic circuits, which evolve over a period of hours before ultimately disappearing into a new electronic state of the graphene. Graphene is also made up of carbon atoms, but in a highly-ordered form.\u003C\/p\u003E\u003Cp\u003EReported in the journal \u003Cem\u003ENanoscale\u003C\/em\u003E, the research was primarily supported by the U.S. Department of Energy Office of Science, and involved collaboration with researchers from the Air Force Research Laboratory (AFRL), supported by the Air Force Office of Scientific Research. Beyond allowing fabrication of disappearing circuits, the technology could be used as a form of timed release in which the dissipation of the carbon patterns could control other processes, such as the release of biomolecules.\u003C\/p\u003E\u003Cp\u003E\u201cWe will now be able to draw electronic circuits that evolve over time,\u201d said \u003Ca href=\u0022http:\/\/www.me.gatech.edu\/faculty\/fedorov\u0022\u003EAndrei Fedorov\u003C\/a\u003E, a professor in the \u003Ca href=\u0022http:\/\/www.me.gatech.edu\/\u0022\u003EGeorge W. Woodruff School of Mechanical Engineering\u003C\/a\u003E at Georgia Tech. \u201cYou could design a circuit that operates one way now, but after waiting a day for the carbon to diffuse over the graphene surface, you would no longer have an electronic device. Today the device would do one thing; tomorrow it would do something entirely different.\u201d\u003C\/p\u003E\u003Cp\u003EThe project began as a way to clean up hydrocarbons contaminating the surface of the graphene. But the researchers soon realized they could use it to create patterns, utilizing the amorphous carbon produced via electron beam \u201cwriting\u201d as a dopant to create negatively-charged sections of graphene.\u003C\/p\u003E\u003Cp\u003EThe researchers were initially perplexed to discover that their newly-formed patterns disappeared over time. They used electronic measurements and atomic force microscopy to confirm that the carbon patterns had moved on the graphene surface to ultimately form a uniform coverage over an entire graphene surface. The change usually occurs over tens of hours, and ultimately converts positively-charged (p-doped) surface regions to surfaces with a uniformly negative charge (n-doped) while forming an intermediate p-n junction domain in the course of this evolution.\u003C\/p\u003E\u003Cp\u003E\u201cThe electronic structures continuously change over time,\u201d Fedorov explained. \u201cThat gives you a reconfigurable device, especially since our carbon deposition is done not using bulk films, but rather an electron beam that is used to draw where you want a negatively-doped domain to exist.\u201d\u003C\/p\u003E\u003Cp\u003EGraphene consists of carbon atoms arranged in a tight lattice. The unique structure provides attractive electronic properties that have led to widespread study of graphene as a potential new material for advanced electronics applications.\u003C\/p\u003E\u003Cp\u003EBut graphene still consists of carbon atoms, and when patterns are deposited on the surface with ordinary carbon atoms, they begin slowly migrating over the graphene surface. The speed at which the atoms move around can be adjusted by varying the temperature or by fabricating structures that direct the movement of the atoms. The carbon atoms can also be \u201cfrozen\u201d into a fixed pattern by using a laser to convert them to graphite \u2013 another form of carbon.\u003C\/p\u003E\u003Cp\u003E\u201cThere are multiple ways to modulate the dynamic state, through changing the temperature because that controls the diffusion rate of carbon, by directing the atomic flow, or by changing the carbon phase,\u201d Fedorov said. \u201cThe carbon deposited through the focused electron beam induced deposition (FEBID) process is linked to graphene very loosely through van der Waals interactions, so it is mobile.\u201d\u003C\/p\u003E\u003Cp\u003EBeyond the potential security applications for disappearing circuits, Fedorov sees the possibility of simplified control mechanisms that would use the diffusing patterns to turn processes off at preset intervals. The technique might also be used to time the release of pharmaceuticals or other biomedical processes.\u003C\/p\u003E\u003Cp\u003E\u201cYou could write information in ones and zeroes with the electron beam, use the device to transfer information, and then two hours later the information will have disappeared,\u201d he said. \u201cInstead of relying on complex control algorithms that a microprocessor has to execute, by changing the dynamic state or the electronic system itself, your program could become very simple. Perhaps there could be certain activated, triggered processes that could benefit from this type of behavior in which the electronic state changes continuously over time.\u201d\u003C\/p\u003E\u003Cp\u003EFedorov and his collaborators have so far shown only the ability to create simple patterns of charged domains in the graphene. Their next step will be to use their p-n junctions to create devices that would operate for specific periods of time.\u003C\/p\u003E\u003Cp\u003EFedorov admits that this dynamic carbon patterning could pose a challenge for electrical engineers accustomed to static devices that perform the same functions day after day. But he thinks that some will find useful applications for this new phenomena.\u003C\/p\u003E\u003Cp\u003E\u201cWe have made a critical step in discovery and understanding,\u201d he said. \u201cThe next step will be to demonstrate a complicated and unique application which would otherwise be impossible to do with a conventional circuit. That would bring a whole new level of excitement to this.\u201d\u003C\/p\u003E\u003Cp\u003ESongkil Kim, a post-doctoral fellow in Fedorov group, was a lead researcher in this work assisted by Georgia Tech\u2019s graduate students M. Russell and M. Henry. Other collaborators on the project include S. S. Kim, R. R. Naik, and A. A. Voevodin from the U.S. Air Force Research Laboratory and S. S. Jang, and V. V. Tsukruk from the School of Materials Science and Engineering at Georgia Tech.\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThis research was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under Award DE-SC0010729 and by the Air Force Office of Scientific Research (AFOSR) through BIONIC Center Award FA9550-09-1-0162. The comments and conclusions are those of the authors and do not necessarily reflect the official views of the DOE or AFOSR.\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ECITATION\u003C\/strong\u003E: S. Kim, et al., \u201cDynamic modulation of electronic properties of graphene by localized carbon doping using focused electron beam induced deposition,\u201d (Nanoscale 7, 14946-14952, 2015). \u003Ca href=\u0022http:\/\/dx.doi.org\/10.1039\/c5nr04063a\u0022\u003Ehttp:\/\/dx.doi.org\/10.1039\/c5nr04063a\u003C\/a\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EResearch News\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EGeorgia Institute of Technology\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003E177 North Avenue\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EAtlanta, Georgia 30332-0181 USA\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EMedia Relations Contact\u003C\/strong\u003E: John Toon (404-894-6986) (\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E).\u003Cbr \/\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EUsing carbon atoms deposited on graphene with a focused electron beam process, researchers have demonstrated a technique for creating dynamic patterns on graphene surfaces. The patterns could be used to make reconfigurable electronic circuits.\u0026nbsp;\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Researchers have demonstrated a technique for creating dynamic patterns on graphene surfaces."}],"uid":"27303","created_gmt":"2015-09-29 10:50:53","changed_gmt":"2016-10-08 03:19:40","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2015-09-29T00:00:00-04:00","iso_date":"2015-09-29T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"453351":{"id":"453351","type":"image","title":"Electron beam writing","body":null,"created":"1449256297","gmt_created":"2015-12-04 19:11:37","changed":"1475895197","gmt_changed":"2016-10-08 02:53:17","alt":"Electron beam writing","file":{"fid":"203411","name":"electron-beam-writing.jpg","image_path":"\/sites\/default\/files\/images\/electron-beam-writing.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/electron-beam-writing.jpg","mime":"image\/jpeg","size":87461,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/electron-beam-writing.jpg?itok=njehdxtp"}},"453361":{"id":"453361","type":"image","title":"Graphene surface","body":null,"created":"1449256297","gmt_created":"2015-12-04 19:11:37","changed":"1475895197","gmt_changed":"2016-10-08 02:53:17","alt":"Graphene surface","file":{"fid":"203412","name":"graphene-surface2.jpg","image_path":"\/sites\/default\/files\/images\/graphene-surface2_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/graphene-surface2_0.jpg","mime":"image\/jpeg","size":93659,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/graphene-surface2_0.jpg?itok=hztMts22"}},"453371":{"id":"453371","type":"image","title":"Graphene doping with carbon","body":null,"created":"1449256297","gmt_created":"2015-12-04 19:11:37","changed":"1475895197","gmt_changed":"2016-10-08 02:53:17","alt":"Graphene doping with carbon","file":{"fid":"203413","name":"graphene-doping.jpg","image_path":"\/sites\/default\/files\/images\/graphene-doping_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/graphene-doping_0.jpg","mime":"image\/jpeg","size":410756,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/graphene-doping_0.jpg?itok=YulTaY9E"}}},"media_ids":["453351","453361","453371"],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"145","name":"Engineering"},{"id":"149","name":"Nanotechnology and Nanoscience"},{"id":"135","name":"Research"}],"keywords":[{"id":"2781","name":"Andrei Fedorov"},{"id":"610","name":"carbon"},{"id":"8458","name":"doping"},{"id":"143131","name":"focused electron beam"},{"id":"429","name":"graphene"},{"id":"52411","name":"p-n junction"}],"core_research_areas":[{"id":"39451","name":"Electronics and Nanotechnology"},{"id":"39471","name":"Materials"}],"news_room_topics":[{"id":"71881","name":"Science and Technology"}],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EJohn Toon\u003C\/p\u003E\u003Cp\u003EResearch News\u003C\/p\u003E\u003Cp\u003E\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E\u003C\/p\u003E\u003Cp\u003E(404) 894-6986\u003C\/p\u003E","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}